Protesters gather outside the BMA meeting that voted to call on the government to scrap its planned NHS reforms. Photograph: Andy Rain/EPA

Doctors have voted to call on the government to scrap its plans for overhauling the NHS.

The health secretary, Andrew Lansley, is coming under increasing pressure over his reforms, which involve the abolition of more than 150 organisations and moving 80% of the NHS budget into the hands of GPs.

Some doctors support the content of the health and social care bill, currently going through parliament, but many have been voicing opposition to parts of it, including increasing the role of private companies in delivering healthcare.

Today the British Medical Association (BMA) held an emergency meeting attended by almost 400 doctors to debate the plans.

Doctors voted in favour of calling on Lansley to withdraw the bill entirely and for a "halt to the proposed top-down reorganisation of the NHS".

They said the government should act on criticisms from those who are opposed to the bill and accept there is "no electoral mandate" for the plans.

The meeting comes after Liberal Democrat delegates rejected the shakeup at the party's spring conference, with members voting not to support the "damaging and unjustified" reforms.

Responding to the vote, the shadow health secretary, John Healey, said: "First the Lib Dems, now the BMA – this is quickly turning into David Cameron's worst NHS week. His damaging plans for the health service are descending into chaos."

Doctors also accused Lansley of using "inaccurate and misleading information to denigrate the NHS", by comparing UK cancer and heart disease rates with those in Europe.

Doctors also voted for the government to recognise that primary care trusts, which face abolition, are losing staff and risk collapse, and for the government not to undermine their current functions.

At the meeting, the BMA chairman, Dr Hamish Meldrum, said the reforms could have "irreversible consequences" and would damage patient care.

He said the NHS was potentially facing the biggest reorganisation of its 63-year history. "The government's proposed reforms have far-reaching and potentially irreversible consequences for how the NHS is run and the way we deliver care to our patients."

He added that it was difficult to argue against some of the government's claimed objectives, including greater involvement of clinicians in decision-making and more information for patients, "but, as on so many occasions, it's the reality not the rhetoric that counts and it's the reality that is causing all the problems".

Meldrum added: "Because what we have seen is an often contradictory set of proposals, driven by ideology rather than evidence, enshrined in ill-thought-through legislation and implemented in a rush during a major economic downturn."

The reforms also face strong opposition from other unions, including Unite and the Royal College of Nursing.

Labour has tabled amendments to the bill, designed to protect the NHS against the introduction of a full-blown competitive market, which the party warned would undermine care, increase bureaucracy and put the future of hospitals at risk.

The shadow health secretary, John Healey, said the amendments would strike out proposals to allow healthcare regulator Monitor to apply the full force of competition law to NHS contracts.

The bill, as drafted, would give Monitor the same powers as the Office of Fair Trading to impose fines of up to 10% of turnover for anti-competitive practices, he said.

And he predicted that private firms would use the measures to mount persistent challenges to deals struck by GP consortiums to commission services from local hospitals or hospices.

Even discussions between GPs and hospitals on the best way to deliver services to patients could be construed as anti-competitive practices, leading to fines or legal action through the domestic and European courts, Healey said.

GP consortiums and NHS hospitals could be forced to spend large sums on lawyers to protect themselves against possible action.

Labour put forward its amendments on Tuesday in the committee stage of the bill, and has called an Opposition Day debate on the issue in the chamber tomorrow.

Healey accused Lansley of keeping quiet about the implications of the competition measures and challenged him to "stand up and defend these changes".

"The more that people see of the changes and look at the risks, the more concerned they become," said Healey. "I am concerned that private companies with big legal departments are going to cause havoc with the ability to plan and run services.

"They could challenge the decisions GPs make to commission services from local hospitals. They could put hospitals at risk. They could prevent the links that we want to see between commissioners and providers of services."